\begin{frame}{定理环境中文或英文显示测试}

{\bf 注意}：如使用 *-cn-ctex.tex, 下面显示~{\bf 定理} 和~{\bf 证明};
如使用 *-cn-xeCJK.tex, 显示 Theorem 和 Proof.

\begin{theorem}
    不存在最大的质数。
\end{theorem}

\begin{proof}
    Suppose $p$ were the largest prime number.
    Let $q$ be the product of the first $p$ numbers, then $q + 1$ is not
    divisible by any of them.
    But $q + 1$ is greater than $1$, thus divisible by some prime number
    not in the first $p$ numbers.\qedhere
\end{proof}
\end{frame}
